Answer-back control circuit



March 1965 R. H. HALVORSEN ANSWER-BACK CONTROL CIRCUIT Filed Jan. 31, 1962 FIG. I II [N I n I l I l I I u c 0 FIGS I I 26 l2 '3-\ :1: IS- fi i l I .J

I II

INVENT OR RALPH H. HALVORSEN ATTORNEY United States Patent 3,176,666 ANWER-BACK CGNTROL CIRCUIT Ralph H. Halvorsen, Des Plaines, IlL, assignor to Teletype Corporation, Slrolrie, IlL, a corporation of Delaware Filed tan. 31, 1962, Ser. No. 170,958 6 Claims. (Cl. 178-41) This invention relates to a control circuit for an answerback mechanism and more particularly to an answer-back control circuit in a teletypewriter having contacts positionable in response to a predetermined sequence of signals either locally or remotely generated.

In a teletypewriter, operation of the local answer-back mechanism can be initiated by either operation of a Here Is key on a local keyboard or upon closure of a set of contacts by instrumentalities responsive to a predetermined sequence of generated signals. Since this predetermined sequence of signals may be either remotely or locally generated and since the answer-back mechanism should operate only in response to remotely generated requests for operation or from the depression of the Here Is key, it is necessary to distinguish between a locally and remotely generated predetermined sequence of signals to assure that the initiation of the operation of the local answenback mechanism is in response only to the remotely generated sequence of characters. Also, because the same predetermined sequence of signals is used to initiate both the local and remote stations answerback mechanism, the local stations answer-back mechanism must be disabled to prevent simultaneous operation of the remote and local answer-back mechanisms which would result in the garbling of the messages.

An object of the invention is to provide a control circuit for an answer-back mechanism for distinguishing between a locally generated sequence of signals and a remotely generated sequence of the same signals.

Another object of the invention is to enable the operation of a local answer-back mechanism either upon receipt of a predetermined sequence of signals from a remote station or upon depression of a local Here Is key while disabling the operation of the local answer-back mechanism upon the sequential depression of the keys of the local keyboard in a sequence that locally generates the same predetermined sequence of signals.

An object of the invention is to break the energizing path to an answer-back trip magnet during operation of the local keyboard except when an answer-back operation is initiated by depression of the Here Is key.

An object of the invention is to provide a control relay energizable by operation of the local keyboard to disable the local answer-back mechanism and de-energizable upon receipt of a remotely generated predetermined sequence of signals.

In accordance with the invention, operation of the keys of the local keyboard momentarily closes a pulsing contact to complete an energizing path for a control relay. Upon energization, the control relay locks to a contact which is opened upon recognition of a predetermined character and opens a contact in a circuit to an answerback trip magnet to prevent operation of the answer-back mechanism which would otherwise occur upon the operation of the keys of the local keyboard in a predetermined sequence but for the opening of this contract by the control relay. Remote generation of the predetermined sequence of characters containing the above-mentioned predetermined character causes the normally closed holding contact to open the locking path of the control relay to assure that it is de-energized and to close the energizing path for the answer-back magnet thereby initiating trans mission of the answer-back message.

Other features and advantages of the invention will 3,175,066 Patented Mar. 30, 1965 become apparent in the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic wiring diagram for the answerback control circuit according to the preferred embodiment of the invention; and

FIG. 2 is a schematic drawing of the answer-back trip magnet and answer-back mechanism.

Referring now to the drawings there is schematically shown in FIG. 2, a conventional answer-back mechanism with an answer-back drum 1d. The answer-back drum 1% is preferably a conventional coded drum having circumferential rows of bars with breakable tines or projections on each bar for permutatively coding. each bar, and is preferably of the type illustrated in Patent No. 2,752,414, issued in the name of Theodore I. Przysiecki.

As in the Przysiecki patent, the present answer-back drum id is driven through an answer-back or message cycle by an engaged clutch which causes repeated stepping of the answer-back drum through a transmission cycle to transmit in succession each of the characters constituting the answer-back message. In the Przysiecki patent a clutch controlling extremity on the bell crank 37 releases the clutch and answer-back drum for repeated operations, and in lieu thereof, as shown in FIG. 2, a trip latch 17 is provided for clockwise rotation during the momentary energization of an answer-back trip magnet 15 thereby releasing a cam sleeve 19 to drive code dr-um 19 with a step by step movement. The cam sleeve 19 has a cam surface thereon for driving a pawl 20 to engage successive tines and step the answer-back drum it) through a complete cycle, whereupon the trip latch 17 again latches the cam sleeve 19 against further rotation, thus stopping the step-by-step movement of drum 1d. During rotation of the answer-back drum 10, sensing code levers 18 sense the permutative coding of tines at each step and are permitted to operate their contacts 21 sequentially to send out the answer-back message over the line. Inasmuch as the claimed invention is directed to the control circuitry for the answer-back trip magnet 15, a more complete description of the answer-back mechanism is not included but may be had by reference to the above Przysiecki patent.

The control circuitry for the answer-back mechanism includes a contact assembly 11 shown in dotted lines in FIG. 1 having a set of normally closed contacts 12 desig nated as the Figures contacts and a set of normally open contacts 13 designated as upper case D contacts. The normally closed contacts 12 are opened by movement of a function bar 14 in response to the receipt of the Figures character in the selector mechanism of the teletypewriter. Conversely, normally open contacts 33 are closed by movement of a function bar 16 in response to a sequential receipt of the Figures and upper case D characters. For a description of a specific type of apparatus (sometimes called a stunt box) for closing a set of contacts in response to a single character or in response to a sequence of characters by a function oar responsive to a selector mechanism, reference is made to United States Patent No. 2,666,095, granted January 12, 1954, to Walter J. Zenner, particularly FIGS. 6 to 14, which patent is hereby incorporated by reference as though fully disclosed herein.

Referring now to FIG. 1, there is disclosed control circuitry that allows the local answer-back mechanism to identify itself to a distance station, which of course, is the usual function of the answer-back mechanism. Manifestly, o her messages such as an end-of-message sequence of characters could be encoded on the drum. Energization of the answer-back trip magnet 15 can be accomplished either by the closure of a normally open Here Is Here Is contact 21 and answer-back trip magnet to positive battery. The circuitry for completing the energizing path to the answer-back trip magnet 15 upon the reception of the sequence of Figures and upper case D characters is from negative battery, conductor 25,

"Figures contacts 12 (reclosed after opening in response to receipt of the Figures code), conductor 26, normally open, now closed, upper case D contact 13, conductor -27, normally closed contact 28, conductor 29, and answerback trip magnet 15 to positive battery.

An answer-back control relay is provided to prevent the operation of the local answer-back mechanism by the sequential depression of the local Figures and upper case D keys and the closing of their associated stunt box contacts while allowing the operation of the answerback mechanism upon the receipt of the remotely generated sequence Figures and upper case D characters with the accompanying closing of the stunt box contacts.

Operation of any of the keys of the local keyboard with a single exception, viz., the Here Is key, closes a normally open keyboard contact 31 in the energizing circuit for the answer-back control relay 30. Upon operation of a key of the local keyboard, the energizing circuit for the answer-back control relay 3a is complete from negative battery, through now closed pulsing keyboard contact 31, the coil of the answer-back control relay 3% and conductor 32 to positive battery.

Release of an operated key is accompanied by an opening of the pulsing keyboard contact 31 and of the energizing circuit for the answer-back control relay 319. However, the answer-back control relay will not de-energize as it is locked up through a circuit extending from negative battery, conductor 25, normally closed Figures contact 12, conductor 33, normally open, now closed, contact 34, conductor 35, the coil of the answer-back magnet 30 and conductor 32 to positive battery. Thus, it should be apparent that the answer-back control relay holding circuit maintains the answer-back control relay 30 energized until suchtime as a Figures character is present in the selector mechanism whereupon the Figures contact 12 in the stunt box contact assembly 11 opens to break the holding circuit of the answer-back control relay 31). Therefore, regardless of whether or not the Figures character is locally or remotely generated, the selector mechanism opens the Figures contact 12, but so long as the answer-back control relay 30 is energized, its normally closed contact 28 is held open thereby breaking the energizing path extending from the stunt box contact assemblage 11 to the answer-back trip magnet 15.

During the sequential depression of the Figures and upper case D keys on the local keyboard the operation of the control circuitry for an answer-back mechanism in accordance with the present invention is as follows:

With the answer-back control magnet 30 de-energized and the contacts in the positions shown in Fig. 1, depression of the Figures key initiates closing of the pulsing keyboard contact 31 and completes the energizing circuit for the answer-back control relay 31 from negative battery over conductor 32 to positive battery whereupon the answer-back control relay 30 energizes and opens normally closed contacts 28 and closes normally open contacts 34. A short time later in a character cycle, the pulsing keyboard contact 31 opens and breaks the energizing circuit for the answer-back control relay 30. The holding circuit for the answer-back control relay 3% is also broken due to the opening of the normally closed Figures contacts 12 by the operation of function bar 14- by the selector mechanism. Thus, since the Figure contacts i 12 have broken the holding circuit for the answer-back control relay 30, this relay is de-energized when the upper case D key is operated.

Depression of the upper case D key closes pulsing keyboard contact 31 completing the circuit for the answerback control relay 30 extending from negative battery, pulsing keyboard contact 31, the coil of the answer-back control relay 3t and conductor 32 to positive battery. The energizing of the answer-back control 30 by the depression of the upper case D key at the local keyboard results in the opening of normally closed contact 28 thereby breaking the energizing circuit for the answer-back trip magnet 15 extending from the stunt box contact assembly 11 over lead 27 and over lead 29 to the coil of the answer-back trip magnet. Hence, even though the sequence of Figures and upper case D characters has been generated, the answer-back trip magnet 15 has not been energized because of the opening of the normally closed contact 28 by the answer-back control relay 30. Thus, the answer-back trip magnet will not be operated even though the contacts 12 and 13 in the stunt box contact assembly 11 have been operated in a sequence that might otherwise cause energization of the answerback trip magnet 15.

Now, assuming that the answer-back control relay 30 is being held energized by its holding circuit from the previous actuation of the local keys, the receipt of a remotely generated Figures character by the local selector mechanism causes the normally closed Figures contact 12 to open and break the holding circuit of the answer-back control relay 313. Therefore, irrespective of Whether or not the answer-back control relay 30 was energized upon the receipt of a first one of the predetermined sequences of characters, the answer-back control relay 30 will be de-energized after the receipt of this first character.

Upon the receipt of a Figures character and an immediately following upper case D character by the selector mechanism, the function bar 16 closes the normally open upper case D contact and completes an energizing path for the answer-back trip magnet 15 extending from negative battery, conductor 25, now closed Figures contact 12, conductor 26, normally open, now closed contact 13, conductor 27, now closed contact 28, conductor 29 and coil of the answer-back trip magnet to positive battery.

Energization of the answer-back trip magnet 15 releases the cam sleeve 19 which in turn, drives the answer back drum 10 for repetitive stepping movement. Between each step of the answer-back drum 10, the sensing levers 18 sense the permutatively arranged tines and cause the sensed permutations to be transmitted out over the line as electrical signals. The stepping of the answerback drum 10 is stopped by the latch 17 engaging the projection on cam sleeve 19 whereby the clutch, not shown, is disengaged and the stepping of the answer-back message drum 10 is discontinued.

Thus, it is seen that in accordance with the invention the answer-back control relay 30 is operable by the local keyboard to distinguish between a locally generated sequence of characters and the same sequence of characters remotely generated, and permits the answer-back trip magnet to be actuated only by the remotely generated sequence of characters.

Although only a specific embodiment of the invention is shown in the drawings and described in the foregoing specification it will be understood that invention is not limited to the specific embodiment described but is capable of modification and rearrangement and substitution of parts and elements without departing from the spirit of the invention.

What is claimed is:

1. In a teletypewriter having a keyboard for controlling signal transmission, answer-back control circuitry for enabling an answer-back mechanism upon receipt of a sequence of predetermined signals from a remote station and for disabling said answer-back mechanism during generation of the same sequence of predetermined signals at the local station comprising: an answer-back magnet energizable to enable the answer-back mechanism, an energizing circuit for said answer-back magnet having contacts operable to complete said energizing path upon receipt of the sequence of answer-back signals from a remote station, an answer-back control relay energized by operation of the local keyboard, and contacts operated by said answer-back control relay which open said energizing path for said answer-back magnet and thereby disable said answer-back mechanism while signals are being generated at the local station.

2. In a teletypewriter, answer-back control circuitry for an answer-back mechanism comprising: an answerback magnet for enabling said answer-back mechanism, an energizing path for said answer-back magnet, a plurality of contacts in said energizing path operable upon receipt of a predetermined sequence of characters to complete said energizing path, an answer-back control relay, an energizing path for said answer-back control relay, a universal contact operated by local operation of the teletypewriter to close said energizing path for sai answer-back control relay, and contacts operated by said answer-back control relay to open said energizing path for said answer-back magnet when said control relay is energized.

3. A control circuit for an answer-back mechanism of a teletypewriter having a keyboard for controlling signal transmission comprising: an answer-back magnet for en- 'abling said answer-back mechanism, a first energizing path for said answer-back magnet, a key operated contact in said energizing path to complete said energizing path upon the operation of said contact, a second energizing path for said answer-back magnet, a plurality of contacts in said second energizing path operable by the teletype- Writer upon receipt of a predetermined sequence of characters to complete said second energizing path, an answerback control relay, contacts operated by said answer-back control relay to open said second energizing path, an energizing circuit for said answer-back control relay, and a universal contact operable by local operation of the teletypewriter keyboard to complete said energizing path for said answer-back control relay and thereby open said second energizing path to disable said answer-back magnet during local operation of the teletypewriter.

4. In a teletypewriter having a keyboard for controlling signal transmission and stunt box contacts permutatively set by function bars operable by a selector mechanism to complete an energizing circuit for an answer-back trip magnet in response to a predetermined sequence of signals and having a contact operable by a Here Is key on the local keyboard to complete an energizing circuit for an answer-back trip magnet, the improvement comprising: an answer-back control relay energizable by use of the local keyboard, contacts operated by the control relay and in the energizing circuit for the answer-back trip magnet which open the energizing path for the answer-back trip magnet to prevent the completion of the energizing circuit therefor, and a locking circuit for said answer-back control relay including one of said contacts operable by said answer-back control relay and one of said stunt box contacts, said locking circuit being completed when said control relay is energized and broken when the selector mechanism responds to the predetermined characters and opens the stunt box contacts included in the locking circult for the answer-back control relay.

5. in a teletypewriter having a stunt box, a local keyboard for controlling signal transmission and an answerback mechanism releasable for operation by an answerbaclc magnet upon the reception of a predetermined sequence of signals in the selector mechanism and the closing of contacts in the stunt box by function bars operable by the selector mechanism, the improvement comprising: a control relay energizable by operation of the local keyboard, a control relay locking circuit including a normally open control relay contact and a normally closed stunt box contact operable by a function bar to hold said control relay energized until the receipt in the selector mechanism of the first of the characters of the predetermined sequence of characters Which causes the function bar to open the normally closed stunt box contact, and a circuit for energizing the answer-back magnet including a normally open stunt box contact closable by a function bar and a normally closed control relay contact whereby operation of the predetermined sequence of characters on the local keyboard results in the answer-back control relay energizing and opening its normally closed contacts in the energizing circuit for the answer-back magnet to disable the answer-back mechanism from operating and whereby reception of a remotely generated sequence of signals in the selector mechanism opens the normally closed stunt box contacts in the locking circuit for the control relay to de-energize the answer-back control relay and closes the normally open stunt box contacts to complete the energizing circuit to the answer-back trip magnet to release the answer-back mechanism.

6. in a teletypewriter having stunt box, a keyboard for controlling signal transmission and an answer-back mechanism releasable for operation by an answer-back magnet upon the reception of a predetermined sequence of signals in the selector mechanism and the closing of the normally open contacts in the stunt box by a function bar operable by the selector mechanism, the improvement comprising: a control relay which opens a normally closed control relay contact and closes a normally open control relay contact, a control relay energizing circuit including a universal contact operated by the operation of the local keyboard, a control relay locking circuit including said normally open control relay contact and a normally closed stunt box contact to hold said control relay energized until the operation of the selector mechanism by the first characters of the predetermined sequence of characters causes a function bar to open the normally closed stunt box contact, and a circuit for energizing the answer-back magnet including said normally closed control relay contact and a normally open stunt box contact closed by a function bar after reception by the selector mechanism of the predetermined sequence of characters.

References Cited by the Examiner UNITED STATES PATENTS ROBERT H. ROSE, Primary Examiner. 

1. IN A TELETYPEWRITER HAVING A KEYBOARD FOR CONTROLLING SIGNAL TRANSMISSION, ANSWER-BACK CONTROL CIRCUITRY FOR ENABLING AN ANSWER-BACK MECHANISM UPON RECEIPT OF A SEQUENCE OF PREDETERMINED SIGNAL FROM A REMOTE STATION AND FOR DISABLING SAID ANSWER-BACK MECHANISM DURING GENERATION OF THE SAME SEQUENCE OF PREDETERMINED SIGNALS AT THE LOCAL STATION COMPRISING: AN ANSWER-BACK MAGNET ENERGIZABLE TO ENABLE THE ANSWER-BACK MECHANISM, AN ENERGIZING CIRCUIT FOR SAID ANSWER-BACK MAGNET HAVING CONTACTS OPERABLE TO COMPLETE SAID ENERGIZING PATH UPON RECEIPT OF THE SEQUENCE OF ANSWER-BACK SIGNALS FROM A REMOTE STATION, AN ANSWER-BACK CONTROL RELAY ENERGIZED BY OPERATION OF THE LOCAL KEYBOARD, AND CONTACTS OPERATED BY SAID ANSWER-BACK CONTROL RELAY WHICH OPEN SAID ENERGIZING PATH FOR SAID ANSWER-BACK MAGNET AND THEREBY DISABLE SAID ANSWER-BACK MECHANISM WHILE SIGNALS ARE BEING GENERATED AT THE LOCAL STATION. 